The invention relates to heat exchangers and particularly to heat exchangers having a tube construction in which a free-floating helical member is disposed in the tube to promote heat transfer. More particularly, the invention has particular application for use with a liquid to air fin-type heat exchangers, double-pipe heat exchangers, and shell-and-tube type heat exchangers. In the present inventor's previously issued U.S. Pat. Nos. 4,564,066 and 4,627,349 there is disclosed apparatus which includes a free-floating helical strip in the tubes of the heat exchangers of various designs. Various structures are shown for retaining these helices in place without restricting their free rotation or the flow of fluids past them. The helices in the previously issued patents were closely fitted to the inside diameter of the respective tubes so that as the helices turned, they scraped away the hydrostatic film which naturally accumulates on any solid surface immersed in a fluid. This film is the largest barrier to heat transfer since fluids have heat conductivities two or three orders of magnitude less than metals from which heat exchangers are constructed. The helical shape was provided to make the scraping edges turn in response merely to the flow of fluid in the heat exchanger tube.
The apparatus described in the noted patents offer significant improvements in heat transfer. It has now been determined that certain further improvements could be made in the apparatus described therein.
It is an object of the invention to provide a screening or filtering action for the fluids being heated or cooled in the heat exchanger.
It is an other object of the invention to provide for easy removal, cleaning, inspection and replacement of the heat exchanger as well as any filtering or screening element.
Another object of the invention is to provide apparatus which will minimize any pressure drops in the fluid being heated or cooled.
Still another object of the invention is to minimize the space required in a shell-and-tube heat exchanger between the bearing surface and the tube-plate of such heat exchangers.
Another object of the invention is to provide apparatus which is less sensitive to high pressures and particularly to rapid changes in pressure.
Yet another object of the invention is to simplify the construction of the apparatus and to make it suitable for more applications.